Nickel liberator cell



1951 s. RENZONI NICKEL LIBERATOR CELL 4 Sheets-Sheet 1 Original FiledMay 18, 1946 INVENTOR.

L 011/3 .5. EE/vzo/w.

ATTORNEYS.

1951 L. s. RENZONI 2,578,839

NICKEL LIBERATOR CELL Original Filed May 18, 1946 4 Sheets-Sheet 2 INVENTOR.

Louis 5. RE/vzo/w.

A T TORNEK 1951 L. s. RENZONI NICKEL LIBERATOR CELL 4 Sheets-Sheet 5Original Filed May 18, 1946 Es xx 5% ATTORNEY.

Dec. 18, 1951 L. s. RENZONI NICKEL LIBERATOR CELL 4 Sheets-Sheet 4Original Filed May 18, 1946 I ATTORNEY.

Patented Dec. 18, 1951 NICKEL LIBERATOR CELL Louis Secondo Renzoni, PortColborne, Ontario, Canada, assignor to The International Nickel Company,Inc., New York, N. Y., a corporation of Delaware Original applicationMay 18, 1946, Serial No. 670,774. Divided and this application March 19,1948, Serial No. 15,925. In Canada April 12,

1 Claim.

The present invention relates to electrolytic cells forelectro-deposition of metals, and, more particularly, to a nickelliberator cell.

In the normal course of recovering nickel by electrodeposition fromelectrolytes containing chloride ions and utilizing soluble anodes, anexcess of nickel enters the system over that amount of nickel which isremoved at the cathode. In such a system of nickel recovery, it isnecessary, in order to maintain a balance between the nickel enteringthe system and the nickel removed at the cathode, to decrease the amountof nickel entering the electrolyte at the :soluble anode withoutdecreasing the amount of nickel removed at the cathode. In systems forrecovery of nickel wherein all-sulfate electrolytes are employed, i. e.,substantially free of chloride ion, the nickel balance of the system :ismaintained by replacing some of the soluble anodes with insolubleanodes. However, the practice of replacing soluble anodes with insolubleanodes to maintain a nickel balance, when rine at the anode, but suchattempts have been l unsuccessful due to difiiculties encountered inhandling the chlorine. Furthermore, to provide adequate cathodeefiiciency for economical operation, it has been found necessary to useeither cathode or anode diaphr-agms to prevent a large percentage of thecurrent from being utilized for hydrogen ion discharge and chlorinereduction. Any such diaphragm arrangements, suitable for nickelelectro-refining, have, however, been found to deteriorate rapidly dueto the action of molecular chlorine, resulting in numerous chlorineleaks, necessitating frequent changes of diaphragms and tank linings.Even more objectionable than the hereinbefore mentioned difliculties hasbeen the resulting addition of chlorinated, water soluble, organiccompounds to the nickel electrolyte which resulted in production ofstrained, warped cathodes throughout the tank house.

It is apparent, therefore, that in order to satisfactorily operate abalanced nickel system, when employing a chloride ion-containingelectrolyte, it would be necessary to provide an electrolysis cell and amethod for operating the cell in a manner whereby chlorine would not beliberated at an insolubleanode during the electrolysis.

In view of the foregoing remarks, it will be apparent that the art ofnickel recovery by electro-deposition, up to the time of the presentdiscovery, was confronted with the problem of obtaining an electrolysiscell that could be operated with insoluble anodes and a chloride-ioncontaining electrolyte in a manner whereby the system could be operatedin balance with respect to nickel, and nickel recovered efliciently at acathode without liberation of chlorine at an insoluble anode.Furthermore, in providing an electrolysis cell that would operate in asatisfactory manner without liberation of chlorine at an insolubleanode, it was desired that the cell operate satisfactorily withoutnecessity of adding cations or anions to the electrolyte system, whichcations or anions would be deleterious to the electrolytic production ofhigh purity nickel at the cathode.

I have discovered a novel liberator cell employin insoluble anodes and achloride-ion-containing electrolyte whereby the electrolytic system canbe operated in balance, with respect to nickel, during electrolysis, andwherein nickel can be recovered by electrodeposition at a cathodewithout liberation of chlorine at an insoluble anode.

It is an object of thepresent invention to provide a liberator cellcapable of maintaining a catholyte substantially free of anolyte andanolyte substantially free of catholyte.

It is still another object of the present invention to provide aliberator cell having an anode compartment and a cathode compartmentseparated by an intervening compartment, 1. e., a middle compartment,whereby during operation of the novel cell, the cathode compartment ismaintained substantially free of anolyte and the anode compartmentmaintained substantially free of catholyte.

The present invention contemplates the provision of a liberator cellhaving an insoluble anode whereby chlorine is not liberated at the anodeduring operation of the cell when employing a chlorine-ion-bearingelectrolyte.

The present invention further contemplates providing a novel liberatorcell for the recovery of nickel by electro-deposition'from achlorideion-bearing electrolyte.

It is within the contemplation of the present invention to provide aliberator cell having insoluble anodes for the recovery of nickel byelectrodeposition from a chloride-ion-bearing electrolyte.

The present invention also ,provides a liberator cell havinginsoluble-anodes for recovering nickel by electrodeposition from achloride-ion-containing electrolyte Without liberation of chlorine atthe insluoble anodes during operation of the cell.

Other objects and advantages of the: present invention will becomeapparent from the following description taken in conjunction with thedrawings in which:

Fig. l is a diagrammatic illustration of an installation such as may beemployed in carrying out the present invention;

Fig. 2 is a sectional view.;taken on line 2-2 of i Fig. 1;

Fig. 3 is a view partly in section of a cathode compartment;

Fig. 4 is a sectional view taken on line 4-4 of Fig. 3;

Fig. 5 is anelevational view of amanifold feed assembly such as may beemployed forfeeding electrolyte to the novel liberatorcellsuch asprovided by the present invention;

- Fig. 6 is a-sectionalelevationalview taken on line 6--6 in Fig. 7 andshowing in detail ofa suitable means of assembly for bus bar connectionsfor anodes and cathodes;

Fig. 7 is a plan view of asuitable means 10f assembly for bus-barconnections for anodes and cathodes;

Fig. 8 isan elevational view of a-nganode compartment frame;

Fig.9 is a-sectional view of Fig. 8; and

Figs; 10 and 11 are elevational views of a cathode and an anoderespectively.

Generally speaking, the-novel apparatus embodying the-present inventioncomprises an electrorefining tank-in-rwhich are suspended a ;plu-

ralityof alternating anodes and :cathodes, each electrode beingcontained within a compartment therefore, eachcompartment comprising adiaphragm at'each side of.-the electrode with suitable frameworkformaintaining the diaphragms in substantially parallel, spaced-apartrelationship and'each compartment being maintained in spaced-@partrelationship with each adjoining compartment by suitable framework thusproviding diffusion zones, i. e., intervening compartments, --betweenadjacent electrode compartments. Anolyte and catholyte are introducedin- ,to the respective anode and cathode compartments at ratessuflicient to provide the hydro- .static heads required in eachcompartment to insure flow .of both anolyte and catholyte into theintervening diffusion :zones, an overflow being provided in thediffusion zone for the mixture of anol-yte and catholyte-at a suitablelevel to assist in maintaining the preferred hydrostatic head.Theanolyte employed is an acid solution substantially devoid of chlorideion and is preferably a dilute sulphuric acid solution, while thecatholyte is a sulphate-chloride-nickel" electrolyte. During operationof .the novel cell, nickel is removed from the catholyte at the cathodeand the electrolyte,depleted in nickel content, flows through thecathode diaphragm tothe middle compartment. At the anode, meanwhile,oxygen is liberated at 100% current efiiciency with the simultaneousliberation of hydrogen ions. The liberation "of hydrogen ions results inthe continuous production of sulfuric acid. Thus, the anolyte passingthrough the anode diaphragm has an increased acid content. Inthe middlecompartment of the cell, the two solutions, 1. e.,

anolyte and catholyte, are mixed to form acid liquor which issubsequently used for pH correction. The mixing of the two liquors inthe middle compartment is not efficient, however, and there is atendency for the heavy liquor from the oathode compartment to segregatenear the tank bottom. For this reason, it is an essential feature of thepresent invention that the overflow from the electro-refining tank betaken off in the lower regions thereof so that this heavy mixture iswithdrawn. The mixture withdrawal outlet will of course be brought tothe proper level for overflow in order to maintain the properrelativelevels within the anolyte and catholyte com- 7 partments and theintervening diffusion zone and this bringing to proper level may be bygooseneck bend or other means Well known to those skilled in the art. Itis also an essential feature of the present invention that infiltrationof the heavyanolyteecatholytemixture into the anolyte compartment shouldbe avoided and for this reason the suspended anodes and anode"compartments should not extend to the bottom of the tank-and in thepreferred embodiment, they should-notextend morethan about two-thirds/3) of the depth of the tank. 'By this arrangementcontactbetween theanodes and the heavy anolyte catholyte mixture with the-undesirableevolution of free chlorine which would result therefrom is avoided.'Itwill'thus be apparent from the foregoing that the port of withdrawalof the heavy-liquor should be preferably in that portion'of the tankbeneath the bottom of the anodes.

Inreference to respective depths of the anode and .cathode compartments,although the tim ferred embodiment of the present invention is that suchcompartmentsshould not extend more than-about two-thirds of'the depth ofthe tank, it is also preferred, but not essential, that thecathodecompartments are of the same depth as the anode: compartments. The depthof the cathode compartments can be varied. however, particularly madedeeper, without materially affecting the operation of the tank. However,I have :foundthat there is no particular advan tage :inemploying a shortanode and a long oathode in carrying out the method of electrolysis forwhich .the'present liberator cell is particularly adapted, although theuse of a cathode longer in length than the anode would be of advantagein :a process requiring a high anode current density and a lower cathodecurrent density.

Referring to the drawings,Fig. 1 is a diagram- 'matic illustration of aninstallation such as may be employed in carrying out the present inven--tion. In Fig. 1, a multi-compartment electrorefining tank 32,containing a mixed acid electrolyte, is shown having suspended in eachof the compartments a plurality of alternating anode compartments 3 andcathode compartments 35 which are more clearly illustrated in Fig. 2.The anode compartments 34 and cathode compartments35 are supported bycompartment-bearing -supports38 in a spaced-apart relationship with eachadjoining compartment whereby a diffusion zone is provided betweenadjacent compartments. Suitable means, such as supports 39 and ill, moreclearly shown in Fig. 2, maintain the comp-art ment-bearing supports 38in desired position. An acid 2 I, substantially free of chloride ions,and preferably concentrated sulphuric acid, is contained in a suitableacid tank 20. By means of gravity, the acid 2| is allowed, to flowthrough a conduit, such as pipe 24, and control valve 23.

into an anolyte supply tank 25 in'which the acid 2| flowing therein isdiluted to provide an aqueous anolyte 26, preferably containing aboutgrams per liter of sulfuric acid. By means of gravity, the anolyte 26 isallowed to flow through a conduit, such as pipe 21 and control orifice28 into the anode compartments 34. Similarly a suitable nickelelectrolyte containing chloride ions and sulfate ions is fed through amain feed line, such as pipe 29 and riser 33 into the cathodecompartments 35. By means of an orifice, such as shown by referencenumeral 3|, the rate of flow of catholyte is controlled to a desiredrate. In order to maintain a hydrostatic head in the anode compartments34 and cathode compartments 35, an overflow system, such as overflowsystem 35, is provided to allow for withdrawal of mixed electrolyteliquor from the tank and diifusion zones in a manner whereby the surfacelevel of the mixed electrolyte solution in the diffusion zones and tankis maintained at a lower surface level than the surface levels of theanolyte in the anode compartments 34 and the catholyte in the cathodecompartments 35. The mixed electrolyte solution flowingthrough overflowsystem 36 flows by gravity through a conduit such as pipe 31 into anacid liquor tank 41 The acid liquor Mat is pumped by a suitable meanssuch as pump 43 through a conduit, such as pipe 44, into a pH correctiontank 45. The acid liquor 4|a may be used for pH correction of purifiednickel catholyte or may be employed for other purposes as desired.

' Fig. 2 is a sectional view taken on line 22 of Fig. 1 and shows thepreferred embodiment of a nickel liberator cell such as contemplated bythe present invention. In Fig. 2, a refining tank 32 is provided havinga suitable lining 33 and an overflow system, such as a goose-neckoverflow system 36. A plurality of alternating cathode compartments 35and anode compartments 34 are suspended in tank 32 in a manner such asshown in Fig. 2 whereby the bottom 4'? of each anode compartment 34rests in a slot 48 of compartment-bearing support 33, and, similarly,the bottom 49 of each cathode compartment 35 rests in a slot 50 ofcompartment-bearing support 38. The compartment-bearing support 38 issupported in the desired position by means of a suitable support system,such as supports 39 and 43. By means of wood spacers 5i incompartment-bearing support 38, the anode compartments 34 and cathodecompartments 35 are spaced apart to provide an intervening compartment52, i. e., diffusion zone, between adjacent anode and cathodecompartments. Each anode compartment 34 has a suitable insoluble anodesuspended therein, such as anode 53, and each cathode compartment 35 hasa suitable cathode 54, such as a nickel starting sheet, suspendedtherein. Each anode compartment 33 comprises a diaphragm on each side ofthe anode, such as anode diaphragms 55, and each cathode compartment 35comprises a diaphragm on each side of the cathode, such as cathodediaphragms 56. The anode compartments 34 have a suitable framework, suchas frame 51, for maintaining the anode diaphragms in substantiallyparallel, spaced-apart-relationship, and, similarly, the cathodecompartments contain a suitable framework, such as frame 53, formaintaining the oathode diaphragms in substantially parallel,spacedapart relationship. As shown in Fig. 2, the anode compartment 34and cathode compartments 35 the preferred embodiment, the anodecompartments 34 and cathode compartments do not extend more than abouttwo-thirds of the depth of the tank. Such an arrangement of the anodecompartments and cathode compartments substantially inhibits theinfiltration of heavy anolyte-catholyte mixture from the interveningcompartments52 into the anode compartments 34, and thus the heavyanolyte-catholyte mixture does not come in contact with the anodes. Theheavy anolyte-catholyte mixture in the intervening compartments 52 iswithdrawn from the lower portion of the tank by means of the overfiowsystem 36. As shown in Fig. 2, the surface level of anolyte in the anodecompartments 33 and catholyte in the cathode compartments 35 ismaintained at a higher surface level than the mixed electrolyte in theintervening compartments 52 and tank 32, this providing a hydrostatichead in the anode and cathode compartments. In other words, bycontrolling the rate of flow of anolyte into the anode compartment andcatholyte into the cathode compartment, and by proper adjustment of theoverflow system 35. the surface level of anolyte in anode compartments34 and the surface level of catholyte in cathode compartments 35 aremaintained at a higher level than that of the mixed acid solution in theintervening compartment 52, thereby providing a hydrostatic head in theanode compartments 34 and cathode compartments 35 with relation to theintervening compartments'52, and providing flow of anolyte and catholyteinto the diffusion zones in the intervening compartments.

Fig. 3 is a view partly in section of a cathode compartment, and Fig. 4is a sectional view taken on line 4-4 of Fig. 3, showing a suitablemeans of assembly for a cathode compartment such as may be employed in anickel liberator tank such as shown in Fig. 2. In Figs. 3 and 4, asuitable cathode bus bar 60 supports the cathode 54 in the compartmentby means of a cathode connection such as shown by the reference numeral59. Reference numeral 58 shows a suitable frame construction for thecompartment for maintaining cathode diaphragms 56 in substantiallyparallel, spaced-apart relationship. The bottom 49 of the cathodecompartment provides for the resting of the compartment in slots ofcompartment bearer-support 38, shown in Fig. 2, for maintaining thecathode compartments in spaced-apart relationship with each adjoiningcompartment, whereby a diffusion zone, i. e., intervening compartment,is provided between adjacent compartments.

Fig. 5 is an elevational viewof a manifold feed assembly such as may beemployed for feeding anolyte or catholyte to the respective compartmentsof the novel liberator cell such as shown in Fig. 2. In Fig. 5, a tank32 having a suitable lining 33 is shown provided with an overflow system36 hereinbefore described in connection with Figs. 1 and 2. A riser 30carries catholyte from a main feed line into a header such as pipe 6| 7which has a series of outlets 62 arranged in a manner such as shown inFig. 5. Risers 33, preferably soft rubber tubes, are connected to eachoutlet 62 on pipe 6| and the free end of each riser 63 is curved overthe top of tank 32 whereby the catholyte flowing through riser 3|], pipe5|, and risers 63 flows into the cathode compartments suspended in tank32. Orifice 3! connecting riser 30 to pipe 6! maintains the rate of flowof catholyte at the desired rate into the cathode do not extend to thebottom of tank 32, and in .75 compartments. For feeding anolyte to theanode compartments 34,-:a;manifold ;system such as hereinbeforedescribed .for the'catholyte feed may be employed. -Thus, in Fig. 5, aconduit such as conduit 21, is shown which carries anolyte, and whichconduit may be connected to a suitable orifice, and assembly of risers,to maintain the desired rate of flow of anolyte to the anodecompartments in a manner similar to the assembly of conduit 36, orifice3 I, pipe 6| and risers 63 for feeding of catholyte to the cathodecompartments.

Fig. 7 is a plan view of the bus bars and electrode suspension means andFig. 6 is an elevation thereof taken on the line 6-6 of Fig. '7 showingthe anode and cathode bus bars and the means for obtaining properclearances for the anode and cathode compartments suspended in the tank.In Figs. 6 and "7, reference numeral 32 shows a multi-compartment tank,having a suitable lining 33, in which compartments the anode and cathodecompartments are suspended as shown in Fig. 2. Cathode bus bar supports,such as wood strips '64, support the cathode bus bars 60. Similarly,anode bus bar supports, such as wood strips 65, support the anode'busbars 66. The anode bus bars 66 and cathode bus 'bars 66 are assembled ina manner, such as shown in Figs. 6 and 7, whereby a spaced-apartrelationship is maintained thereby providing the intervening compartment52, shown in Fig. 2, between adjacent compartments. Furthermore, Figs. 6and 7 show a suitable means of assembly for current carrying members61A, connecting to anode bus bars 66, which carry current to the anodebus bars. Similarly, current carrying members 6113, connecting to thecathode-bus bars 60, carry current to the cathode bus bars.

In my practice of the present invention, the electro-refining tanks,such as the multi-cell tank of Fig. 7, are connected to each other inseries and a plurality of such tanks connected in this mannerconstitutes an electrical circuit. With reference to Fig. '7, in thetank cell 32A, the anode bus bars 66 are in'contact with the'anodecurrent carrying members 67A. The cathode bus bars 60, in tank cell 32A,are not in contact with a cathode current carrying member, but only witha conductor, i. e., copper, such as shown by reference numeral 68,having no outside electrical contacts. The conductor 68 serves todistribute the current uniformly and to form an electrical contactbetween the two tank cells, i. e., 32A and 32B, such as shown in Fig. 7.Conversely, in tank cell 32B, the cathode bus bars 66 make contact withcathode current carrying member 61B, and the anode bus bars 66 contactconductor 66. Thus, in an arrangement such'as shown by Fig. '7,considering the flow of current through the solution from anodeto'cathode, the current entering at the anodes in tank cell 32A flowsthrough the solution to the cathodes in tank cell 32A, and out throughthe cathode bus bars in tank cell 32A to conductor 68. Thence, thecurrent flows through the anode bus bars 66 and anodes in tank cell 323,through the solution to the cathode, and through the cathode bus bars 60to cathode current carrying member 613.

Fig. 8 is an elevational view, and Fig. 9 is a sectional view of ananode compartment frame such as may be employed in practicing thepresent invention. In Figs. 8 and 9, reference numeral 34 shows asuitable anode compartment having diaphragms 55 maintained, in themannershown, in substantially paralleL'spaced-apart relationship. Fig. 11 isan elevational view of an anode 53, attached by suitable means, such aslugs 54, to an anode bus bar 66. In my practice of the presentinvention, an anode assembly such as shown in Fig. 11 is suspended in ananode compartment frame such as shown in Figs. 8 and 9 to comprise ananode compartment for suspension in a tank, such as tank 32 in Fig. 2.

Fig. 10 is an elevational view of a cathode assembly comprising cathode54 attached by suitable means, such as cathode connection 59, holdingthe cathode to the bus bar 60. In my practice of the present invention,the cathode assembly shown in Fig. 10 is suspended in the oathodecompartment in a manner such as shown in Figs. 3 and 4.

The anode employed in the anode compartments of the novel liberator cellof the present invention is an insoluble anode, satisfactory examples ofwhich are lead anodes or other types of insoluble anodes normallyemployed with allsulfate electrolytes in processes for recovery ofnickel. In my practice of the present invention, I prefer to employ leadanodes containing about 6% antimony, as I have found that these anodesperform satisfactorily and lead is not added to the electrolyte systemas a result of the use of such anodes.

The diaphragms employed for the anode and cathode compartments of thenovel liberator cell are generally of the acid-resistant type. In mypreferred embodiment of the present invention, a duraklad fabric ofvinyl resin is employed for the anode and cathode compartmentdiaphragms. Still another type of diaphragm that has been found to besatisfactory in practicing my invention is a diaphragm consisting ofglass cloth.

In practicing the present invention, when during operation of the cellit is desired to remove the anodes and cathodes from their respectivecompartments, the anodes and cathodes are removed singly from thecompartments by suitable means, such as a traveling crane, the hook ofwhich is attached to the anode or cathode bar of the electrode to beremoved and the electrode is lifted out of the compartment. Similarly,anodes and cathodes are lowered into place singly into the respectivecompartments.

The cathodes employed in the cathode compartments of the novel liberatorcell may be of suitable types generally used in electro-winning ofnickel by electrodeposition. In my preferred embodiment of the presentinvention, I employ nickel starting sheets, such as are well known tothose skilled in the art, for the cathodes in the cathode compartments.

For the purpose of giving those skilled in the art a betterunderstanding of .the operation of the'novel liberator cell, forinstance in the recovery of nickel from an illustrative electrolytecontaining nickel ions and chloride ions, the following description isgiven:

The catholyte employed in the liberator cell embodying the presentinvention can be an aqueous electrolyte containing nickel ions andchloride ions. The anolyte can be an aqueous acid solution substantiallyfree of chloride ions. A suitable anolyte is an aqueous solutioncontaining sulphuric acid. The acid content of the anolyte is determinedby the acid requirements of the electrolyte system as a whole butsufficient acid should be present to make the anolyte a good conductor.In my practice of the present invention, the acid requirements of thesystem are such that the acid concentration of the anolyte is maintainedat about 10 to 20 grams per liter of sulphuric acid, and preferablyabout grams per liter. I employ an aqueous anolyte containing about 10grams per liter of H2804 as I have found that at this acid.concentration, the conductivity of the anolyte is satisfactory. In otherapplications, wherein the acid requirements of the system may begreater, the acid concentration of the anolyte may be proportionatelyincreased. The upper limit of acid concentration in the anolyte in anyapplication is determined by the corrosive action of the mixed acidelectrolyte formed in the middle compartments, such as middlecompartments '52 in Fig. 2. For most practical purposes, an anolytecontaining up to about 50 grams per liter of H2SO4 has been found to besatisfactory.

The anolyte is preferably maintained at a temperature of about 100 F. to140 F. as when temperatures exceeding about 140 F. are employed, thediaphragm fabrics and tanks linings may be deleteriously affected. Lowertemperatures than about 100 F. may be employed, but use of such lowertemperatures results in higher power consumption in the operation of theillustrative novel process described herein for recovery of nickel. Atemperature range of about 120 F. to 130 F. has been found to besatisfactory for the anolyte, as use of temperatures within this rangeprovides the desired results and also allows for absorption of heatgenerated in the event that local short circuits may occur in thesystem.

In my particular application of the illustrative process, currentdensities within the range of about to 50 amperes per square foot havebeen found to be entirely satisfactory, and, preferably, are employed inthe present illustrative process. Although current densities less thanabout 20 amperes per square foot may be employed, the use of such lowercurrent densities necessitates employing a large number of tanks toremove the desired quantity of nickel. As for current densitiesexceeding about 50 amperes per square foot, I have found that use ofsuch high current'densities results in production of exceedingly roughcathodes, and therefore, it is preferred that a current density of lessthan about 50 amperes per square foot may be employed.

In general, the catholytes that may be employed in practicing thepresent invention are similar to those set forth in my U. S. Patent No.2,394,874 relating to the electro-refining of nickel withsulfate-chloride electrolyte. Thus, an aqueous catholyte that can besatisfactorily employed'in the operation of the novel liberator cell ofthe present invention contains about 40 to 60 grams per liter of nickel,about 27 to 30 grams per liter of chloride ion, and about 71 to 120grams per liter of sulfate ion. The pH of the catholyte is preferablymaintained at pH 4.0 to 5.0 at a temperature of 100-l20 F. In thepresent illustrative example, I employ an aqueous catholyte having thefollowing composition:

Constituent Grams per liter about to 60.

about 20 to 30.

about 27 to 30.

about 71 to 120.

about 15 to 25.

about 0.001 to 0.01.

about 0.0001.

about 0.0002 to 0.0005.

about 0.0001.

about 0.0001.

Although the exact nature of the phenomena explaining the conductancemechanism ,forthe satisfactory performance of the novel liberator cellhas not been definitely ascertained, it is believed that the followingdiscussion will be helpful in understandin the principles underlying theconductive mechanism providing for the novel results obtained byemploying the present invention. In the cathode compartment of the novelliberator cell, the conditions to be fulfilled to allow the flow ofcurrent through the catholyte are that either cations or anions or bothanions and cations pass through the cathode diaphragm. In the presentnovel cell, the condition is imposed that all the current must becarried through the cathode diaphragm by the anions. This, I believetakes place in the following manner: at the instant of discharge of anickel ion, giving up its two positive charges, a sulfate anion or twochloride anions must migrate out of the cathode compartment to maintainionic equilibrium within the compartment. This flow of free anionsthrough the diaphragm constitutes a flow of electrons or negativeelectricity towards the anode. Similarly, at the anode compartment, thecondition is imposed that all the current must be carried through theanode diaphragm by the cations. The mechanism, I believe, is as follows:within the anode compartment, oxygen is liberated at the anode at 100%current efficiency as a result of hydroxyl ion discharge. At the instantof discharge of a hydroxyl ion, giving up its unit of negative charge, ahydrogen ion carrying a unit of positive charge must migrate through theanode diaphragm to maintain ionic equilibrium within the compartment.The continuous flow of these free positive ions towards the cathodeconstitutes a flow of positive electricity. Combining the twocompartments by placing between them a middle compartment containing anelectrolyte constitutes an electrolytic cell, the overall operation ofwhich may be described as follows: in the middle compartment, the ionsare free to move under the influence of the electric current and thecations will migrate towards the cathode while the anions will move inthe opposite direction. The fraction of the total current carried byeither the cations or the anions will be determined by theirrespectivemobilities. Thus, when current is flowing through the cell, there is atransfer of cations in the direction of the cathode and of anions in thedirection of the anode. At any given plane in the middle compartment,the net transfer of cations at the plane is equivalent to the sum of thecations migratin into the plane and of the cations migrating out of theplane. The quantity of matter transferred must be equivalent to one Iequivalent weight per faraday. There is, therefore, a boundary ofcations moving towards the cathode and a similar boundary of anions ad.-vancing towards the anode. In the vicinity of either diaphragm, theadvancin boundaries of anions and cations meet a flow of oppositelycharged ions which stream through the diaphragm, and a narrow diffusionzone is thus set up in the immediate vicinity of both diaphragms. Thesediffusion zones form the actual boundaries between the electrodecompartments and the middle compartment. At these boundaries, a freeexchange of ions can take place and the electrical circuit is completedbetween the anode and the cathode. Hence, it may be considered that thediaphragms act as mechanical barriers preventing the diffusion of ions,while the diffusion zones form the permeable boundaries which allow thefree ionic exchange and thus allow for an unhindered flow of current.Although the believed reasons hereinbefore given for the novel resultsobtained by the operation of the present invention are recited above, itis to be understood that the theory for these reasons may change.However, regardless of the reasons underlying the improved resultsobtained with the present invention, it has been found that theemployment of the novel cell provides for efficient recovery of nickelat a cathode from a cloride-ion containing electrolyte withoutliberation of chlorine at insoluble anodes.

In order that those skilled in the art may have a still betterunderstanding of the present invention, the following specific exampleis given, employing a novel liberator cell, such as described in Fig. 2,for recovery of nickel from a sulfatechloride nickel electrolyte withoutliberation of chlorine at the anode.

Ewdmple In an arrangement, such as shown in Fig. 2, an electro-refiningtank having an overflow system is filled with a mixed acid electrolytein the following manner:

An aqueous solution containing about grams per liter of sulfuric acid isrun into the tank until the liquor level reaches the top of thecompartment supports 38. Anolyte, an aqueous solution containing about10 grams per liter of sulfuric acid, is then introduced into the anodecompartments 34 and catholyte, i. e., an aqueous solution containingsulfate, chloride and nickel ions, is introduced into cathodecompartments 35. Both anolyte and catholyte are introduced into therespective compartments at rates of flow sufiiciently rapid to maintainan adequate flow through the respective diaphragm to preventinfiltration of foreign ions into the anode and cathode compartments.Sulfuric acid solutions, similar to that introduced into the tank, areintroduced into the middle compartments 52 at the same time as theanolyte is introduced into the anode compartments and catholyte into thecathode compartments, at a reduced rate of flow to maintain the liquorlevel in the middle compartments below the liquor levels in the cathodeand anode compartments, i. e., such as about 2 inches below the liquorlevels in the anode and cathode compartments. As soon as the liquorlevels in the three compartments, anode compartments 34, cathodecompartments 35 and middle compartments 52, have reached the desiredoperating levels, the flow of sulfuric acid solution to the middlecompartments is stopped and the flow of anolyte and catholyte is allowedto proceed at the desired rates through the respective orifices. foroperation. The anode compartments, containing 6% antimony-lead anodes,and cathode compartments, containing nickel starting sheets as cathodesare arranged in the tank in the manner shown in Fig. 2. of the presentinvention, the novel liberator cell contains 24 cathode and 25 anodecompartments. A one inch space separates the anode compartments from thecathode compartments and the intervening spaces constitute the middlec'ompartments.

The purified nickel electrolyte containing about 56-57 grams per literof nickel, 27-30 grams per liter of chlorideion and 71-120 grams perliter of sulfate ion is fed into the cathode compartments at a rate of300 milliliters per minute while an aqueous solution containing 10 gramsper liter of H2804 is fed into the anode compartments at a rate of 500milliliters per minute. During operation of the cell, the mixed acidliquor from the The tank is then ready In a preferred embodiment 12middle compartments and tanks is continuously removed by' means of theoverflow system. The rate of flow of anolyte at about'500 millilitersper minute into the anode compartments, and catholyteat'300' millilitersper minute into the cathode compartment'has been found to be asufiicientrate of flow to provide a hydrostatic head in thesecompartments with respect to the intervening compartments and to providea flow of anolyte and catholyte into the intervening compartments.

The satisfactory rate of flow of anolyte into the anode compartments andcatholyte into the oathode compartments; whereby a hydrostatic head ismaintained in these compartments with relation to the electrolyte in theintervening compartments to insure flow of anolyte and catholyte intothe intervening compartments is determined by taking into considerationfactors influencing maintaining of the hydrostatic head. Such factorsinclude the relative depth of the electrode compartments and theintervening compartments, the specific gravities of the anolyte andcatholyte, and the porosity of the diaphragms.

The temperature of the anolyte and catholyte is maintained at about 130F. The total current flowing through the tank is 6500 amperes and avoltage of 6.5 volts providing an anode and cathode current density ofapproximately amperes per square foot.

During operation of the cell, the catholyte containing 56-57 grams perliter of nickel, flows to each cathode compartment at 300 millilitersper minute. At each cathode, 4.9 grams of nickel are removed fromsolution per minute. Thus,

' the depletednickel electrolyte flowing through the cathode diaphragmhas a nickel content of approximately grams per liter. At each anode,oxygen is liberated at current efiiciency with a simultaneous liberationof hydrogen ions. This results in the production at each anode oi aquantity of acid equivalent to 7.9 grams of H250. per minute. Sinceanolyte containing 10' grams per liter of IIZSOd flows to each anodeeompartment at the rate of 500 milliliters per minute, theanolytefiowing through the anode diaphragm has a total acid contentequivalent to 25.8 grains per liter of H2SO4.

The anolyte and catholyte flowing through the diaphragm are mixed in themiddle compartments to form an acid electrolyte liquor containingapproximately 15 grams per liter of nickel and 16 grams per liter ofH2804. The acid liquor flows from the tank by means of the overflowsystem and is used for pH correction of the purified nickel electrolyteand replaces an equivalent quantity of H2804 which would otherwise berequired for the purpose. In my operation of the present invention, eachnickel liberator cell of the type shown in Fig. 2, operating at a totalcurrent of 6500 amperes, removes approximately 375 lbs. of nickel perday from the electrolyte system and produces a quantity of acidapproximately equivalent to 625 lbs. of H2SQ4 per day. Duringelectrolysis, heavy liquor infiltration from the middle compartmentsinto the lower portions of the anode compartments is substantiallyeliminated, and thus, the anode compartments are substantially free ofchloride ions, and as a result, chlorine is not liberated at the anode.Hence, nickel is removed efiiciently at the cathodes without liberationof chlorine at the anodes.

The present application is a division of my co pending patentapplication Serial No. 670,774, filed on May 18, 1946, now U. '8. PatentNo. 2,480,771.

Although the present invention has been described in conjunction withcertain preferred embodiments thereof, those skilled in the art willreadily recognize that variations and modifications can be made. Suchvariations and modifications are to be considered to be within thepurview of the specification and the scope of the appended claim. Thus,although the present invention has been described in conjunction with amulti-cell arrangement, as shown in Figs. 1 and 2, it is within thescope of the present invention to include unit nickel" liberator cells,as for example a liberator cell comprising a suitable receptacleprovided with a suitable overflow and having an anode compartment andcathode compartment suspended therein separated in a manner whereby thespace separating the two compartments constitutes a middle compartment,thereby forming a 3-compartment cell.

I claim:

An electrolytic cell for recovering nickel from chloride-bearingcatholyte and employing sulfate anolyte, which comprises; an acidresistant tank; a separate and independent acid-resistant anodecompartment having substantially vertical porous diaphragm side wallsand a substantially vertical anode electrode therebetween insoluble insulfate electrolyte; a separate and independent acidresistantcompartment having substantially vertical porous diaphragm side wallsand a substantially vertical cathode electrode therebetween; saidcompartments being supported in substantially vertical, parallel, spacedapart relation within substantially the upper two-thirds region of saidtank; conductor means for supplying electric current to said electrodes;means for feeding anolyte and catholyte continuously at a regulated rateto their respective electrode compartments including a conduit providedwith an orifice located within and near the top of each compartment,whereby the anolyte and catholyte LOUIS SECONDO RENZONI.

REFERENCES CITED The following references are of record in the v file ofthis patent:

UNITED STATES PATENTS Number Name Date 442,333 Roberts Dec. 9, 1890679,984 Palas et al Aug. 6, 1901 2,277,091 Feyens Mar. 24, 1942 FOREIGNPATENTS Number Country Date 9,563 Great Britain of 1900

